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Paper: Beneath the Baselines: Detecting Molecular Emission from Submillimeter Galaxies with the GBT
Volume: 375, From Z-Machines to ALMA: (Sub)Millimeter Spectroscopy of Galaxies
Page: 157
Authors: Hainline, L.J.; Blain, A.; Greve, T.; Chapman, S.; Smail, I.; Ivison, R.J.
Abstract: We report the first detection of a submillimeter galaxy (SMG) in CO(1 →0) emission using the GBT. We identify a line with ΔvFWHM ∼ 1000 kms−1 in the 1 cm spectrum of SMM J13120+4242 at z = 3.408, which is significantly greater than the width of the previously detected CO(4 →3) line. If the observed CO(1 →0) line profile arises from a single object and not several merging objects, the CO(4 →3)/CO(1 →0) brightness temperature ratio of ∼ 0.26 suggests n(H2) > 103 cm−3 and the presence of sub-thermally excited gas. The 10σ integrated line flux implies a cold molecular gas mass M(H2) ∼ 1011MSolar, comparable to the dynamical mass estimate and four times larger than the H2 mass found from the CO(4 →3) line. While our observations confirm that this SMG is massive and highly gas-rich, they also suggest that Jupper > 3 transitions of CO may not accurately trace cold, diffuse molecular gas in SMGs.
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